Device for producing a leno selvedge, in particular for shuttleless looms

ABSTRACT

Device for producing a leno selvedge, in particular for a loom, including an electromotor with a rotor, whereas the rotor has at least two spaced guide elements for the leno threads, whereas the guide elements are designed as being elastic and flexible so that they can compensate fluctuations in thread tension in direction of the electromotor&#39;s, axis.

BACKGROUND OF THE INVENTION

1. Field of the Invention.

This invention relates to a device for producing a leno selvedge, inparticular for a loom, including an electromotor with a rotor, whereasthe rotor has at least two spaced guide elements for the leno threads.

2. Description of the Prior Art.

A device for producing a leno selvedge is known out of FR-A 23 90 524,this device having arms being elastic and flexible in axial direction.This device is a so-called "planet rotator." Due to its design, such aplanet rotator has a high mass, still increased by the fact that thisknown planet rotator has the spools for the leno threads arrangeddirectly on the rotator. That means that such a device has a mass so bigthat it is physically impossible to accelerate and slow down in shorttime intervals.

The same applies to DE-A 15 35 579 which also shows a so-called planetrotator. This device too is incapable of fast acceleration and fastslowing down due to the movable mass. No other evaluation can be made ofU.S. Pat. No. 2,918,092 since the device also associates the yarn spoolswith its movement.

A device as mentioned above is known out of DE-PS 44 05 776. Hereby, anelectrically drivable servomotor is provided which drives a doup disc,the doup disc forming the rotor of the electrically drivable servomotor.The stator itself is mountable onto the loom by means of a carryingelement, preferably in a free space between the longitudinal braces andthe healds in front to the first heald frames of the loom. Moreparticularly the doup disc, which forms the rotor of the electricallydrivable servomotor, has two opposite openings through which one lenothread at a time is led, these openings serving as guide elements. Thisknown rotator for producing a leno selvedge in a loom works so that itcompletes several hundred revolutions in one direction and ties off oneweft thread after each revolution. A full leno selvedge is thusachieved. On the feeding side of the two leno threads, the leno threadsare twisted according to the number of revolutions of the doup disc sothat, in order to undo this twisting, an inversion of the doupingdirection is indicated, the douped disc having to rotate in exactly theopposite direction. The number of revolutions in either direction hashereby to be the same in an average period of time. If the doupingdirection were not inverted, the leno threads would, some time or other,tear due to the increasing tension occasioned by the growing twisting.

In case of the known fast-running looms making up to 1200 werfts perminute, it was ascertained that after approximately 100 to 1000revolutions in one direction an inversion of the douping directionshould occur. That means that, according to the state of the art, therotor and thus the douping disc of the electrically drivable servomotorhas to be reversed every 10 to 100 second. Due to the number of strokesof a loom, the time available for inversion is of 100 millliseconds(msec) maximum. That means that the rotor of the motor has to standstill and to rotate in the reversed douping direction at full speedwithin 100 msec. Due to the high mass of the douping disc and of therotor respectively, this performance can be achieved with known motorsonly at high cost. The idea to reduce the moved mass of the motor bychoosing a rightaway smaller motor will naturally arise. The dangerincurred in this case is that, if the rotor and thus the douping discare given a smaller diameter, the shedding occurring between the twoleno threads guided through the douping disc is not sufficient, so thatthe weft thread cannot be inserted accurately. Moreover, the threads canstill stick together, impeding the formation of a clean selvedge.

Moreover, during the rotation of the guide elements, the thread tensionof the leno threads guided through the guide elements fluctuates. Thefluctuations depend on the thread length of the leno threads, themselvesdepending on the douping angle and on the coning angle of the devicerelative to the loom. The fluctuations in the thread tension may bringsensitive yarns to tear.

SUMMARY OF THE INVENTION

The object of the invention is therefore to develop a device of theabove-mentioned type, so that on one hand it has a small mass in orderto be able to produce a correct full leno selvedge even in fast runninglooms, and that it additionally is able to compensate fluctuations inthe thread tension of the leno threads, avoiding thus the tear of thethreads.

The solution of the object is to design the guide elements as armsprovided at their ends with eyes through which the leno threads arepassed, the arms being elastic and flexible in axial direction of theelectromotor in order to compensate the thread tensions.

Thanks to the elastic flexibility of the guide elements in the axialdirection of the rotating element and to the corresponding deformationof the guide elements, the otherwise occurring fluctuations in threadtension of the leno threads are compensated.

To untwist the leno threads, the rotating direction of the rotor of theelectromotor is invertable.

The elastic and flexible arms are advantageously provided at their endswith eyes through which the leno threads are passed. The arms themselvescan be of light design, since they are hardly ever subjected to stress.They thus represent a relatively neglectable mass. That means that asmall motor with a correspondingly smaller rotor can be chosen, the massbeing accordingly small, since, due to the arrangement of the arms onthe rotor, the technical designer is now free, except for the outputrequirements, to choose the size and the diameter of the motor. That'swhy motors with a small diameter and with accordingly small moved massescan be used without risking to impede a correct shed aperture, since thelength of the arms arranged on the rotor permits to choose freely thespacing of the eyes in the arms and thus the size of the shed aperture.Thus it is also possible to untwist the leno threads by designing therotor so that its rotating direction is invertable.

The arms are arranged on the rotating element, being thereby essentiallyperpendicular to the rotation axis of the rotating element and standingthus radially out, like a propeller's wings. In order to assure that thearms, depending on the position of the heald frame, are always able totake the best position provided for by the actuation of the device, ithas been foreseen that the arms are stiff in circumferential direction.

According to an advantageous characteristic of the invention, the rotorhas, in the area of its rotational axis, an advantageous centricalboring for passing the leno threads. That means that the leno threadscan be passed through the rotating element by a boring providedcentrically on it, improving thus the thread guiding, particularly withregard to a possible twisting in the area of the boring in the rotor.

More particularly, the arms are arranged on the front side of the rotorof the electromotor, this side facing the material; hereby each arm isdesigned as a hook at its ends, whereas the eye for passing the lenothreads is provided in the area of the hook-shaped curve. The eye can beprovided with inserts that reduce wear and tear of the eye due to theguiding of the leno threads; sleeve-like inserts made or ceramicmaterials have particularly been thought of.

According to another characteristic of the invention, the electromotortogether with the rotor is arranged onto the loom in such a way that therotational axis runs either parallel or in an angle of up to 90° to thewarp threads. Particularly when the angle nearly reaches 90°, the deviceis optimally bought directly to the material edge so that a lenoselvedge can also be executed at the very end of the material. Accordingto still another characteristic of the invention, it may be necessary toarrange further arms accordingly on the opposite front side of the rotorparallel to the arms arranged on the front side facing the material.These additional arms may become necessary in order to guarantee acorrect twisting of the leno threads in the area of the feeding of theleno threads from the spools. This is necessary in order to permit toundo the twisting of the leno threads in the same way as they weretwisted in the feeding area of the threads from the spools by invertingthe rotational direction of the rotor of the electromotor. Thisdifficulty does not arise when the rotor is arranged with its rotationalaxis parallel to the warp threads of the loom.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more details according to the drawings.

FIG. 1 is a diagram showing the nearly perpendicular arrangement to thematerial of the device according to the invention, whereas the healdsand the reed have been omitted in order to guarantee a greaterclearness;

FIG. 2 is a diagram showing the device, the rotational axis of the rotorrunning parallel to the warp threads;

FIG. 3 shows the electromotor with rotor at an angle of approximately45° to the warp threads;

FIG. 4 shows the binding diagram of a full leno selvedge.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In the device 1 shown in the FIGS. 1 to 3, a motor referred to as awhole with numeral 10 is provided, which has a centrical boring 11 forpassing the leno threads 20, 30. In the embodiment shown in FIG. 1,where the rotational axis is transversal to the warp threads 40, thatmeans that it runs essentially parallel to the weft threads 50, twopairs of arms 60, 70 are provided. Each pair of arms 60, 70 consists oftwo arms 61, 62 and 71, 72 respectively. The two pairs of arms 60, 70are running parallel to each other and are fastened each on the frontside of the rotor 10, as can clearly be seen on FIG. 1. The arms 61, 62and 71 72 resp. are hook-shaped and have in the area of the hook-shapedcurve the eyes 73, 74 and 63, 64 resp. These eyes serve for passing theleno threads 20, 30, which are unwinded from the thread spools 80, 90.

Moreover, the arms 61, 62 and 71 resp. are designed in axial direction(arrow 200) of the rotating element 10 as being elastic and flexible inorder to be able to compensate fluctuations in the thread tension.

When the pairs of arms 60, 70 are rotating, a full leno selvedge 100 isexecuted in the are of the material (FIG. 4). In the area where the lenothreads 20, 30 are fed from the yarn spools 80, 90, the threads (at 110)are also twisted, and untwisted again when the rotating direction of therotors is reversed after a given number of revolutions in one direction.The weft threads 50 are inserted between the leno threads and preventthe leno selvedge 100 from untwisting. That means that even whentwisting 110 is untwisted, on the other side, in the area of thematerial, another selvedge is executed by twisting with thecorresponding weft threads.

The device is working in such a way that the rotor of an electromotor isdriven so that its rotation is synchron with the moving of the heald. Asan option it is also possible to achieve an early tying by offsettingcorrespondingly the phases in the synchronisation between the rotationalmovement of the rotor and the heald movement. That means that such adevice is working independently of the heald which is not the case withselvedge machines accommodated on the heald frames.

In the arrangement of the rotational axis running parallel to the warpthreads 40 and shown in FIG. 2, where the healds are referred to withnumeral 130 and the reed with numeral 140, only little problemsnaturally occur when the leno threads 20, 30 are fed into the device. Inthe position of the rotor relative to the material as it is shown inFIG. 2, the spacing form the material is quite big, so that the lenoselvedge cannot be arranged directly on the material.

The selvedge can be arranged much nearer to the material when the deviceis brought into the position according to FIG. 3. Here, the device ispositioned at an angle of approximately 45° to the material. Herebythough, a thread guiding element 120 designed as a reel or a roller isprovided which makes it possible to guide the threads to the material inorder to achieve a correct shed aperture.

The tying which is made with such a device (FIG. 4) is a so-called fullleno tying, that means that each weft thread is completely tied off bythe tying. Although only three threads are involved, such a selvedge isextremely solid and is not too thick thanks to the use of only threethreads, so that the material does not lay thick on the beam in the edgearea, and thus does not lose its shape.

What is claimed is:
 1. Device for producing a leno selvedge,particularly for a loom, including an electromotor with a rotor, whereasthe rotor has at least two spaced guide elements for passing the lenothreads, characterized in that the guide elements are designed as armswith eyes at their ends for passing the leno threads, the arms beingelastic and flexible in axial direction of the electromotor in order tocompensate the thread tensions.
 2. Device according to claim 1,characterized in that the arms are stiff in circumferential direction.3. Device according to claim 1, characterized in that the rotor of theelectromotor has a boring in the area of its rotational axis for passingthe leno threads.
 4. Device according to claim 2, characterized in thatthe boring for passing the leno threads is arranged centrically in therotor.
 5. Device according to claim 1, characterized in that at leastone of said arms is designed at its ends as a hook, whereas the eye isprovided in the area of the hook-shaped curve.
 6. Device according toclaim 1, characterized in that the arms are arranged on the front sideof the rotor of the electromotor, this side being directed towards theselvedge.
 7. Device according to claim 1, characterized in that furtherarms are provided on the opposite front side parallel to the armsarranged on the front side facing the selvedge.
 8. Device according toclaim 1, characterized in that the electromotor together with the rotoris adapted to be arranged onto the loom in such a way that therotational axis runs either parallel or in an angle of up to 90° to thewarp threads.
 9. Device according to claim 1, characterized in that thearms are arranged on the rotor, being thereby perpendicular to therotation axis of the rotor of the electromotor and standing radiallyout.
 10. Device according to claim 1, characterized in that the rotatingdirection of the rotor is reversible.